Retinal blood flow in critical illness and systemic disease: a review

Abstract

Background Assessment and maintenance of end-organ perfusion are key to resuscitation in critical illness, although there are limited direct methods or proxy measures to assess cerebral perfusion. Novel non-invasive methods of monitoring microcirculation in critically ill patients offer the potential for real-time updates to improve patient outcomes. Main body Parallel mechanisms autoregulate retinal and cerebral microcirculation to maintain blood flow to meet metabolic demands across a range of perfusion pressures. Cerebral blood flow (CBF) is reduced and autoregulation impaired in sepsis, but current methods to image CBF do not reproducibly assess the microcirculation. Peripheral microcirculatory blood flow may be imaged in sublingual and conjunctival mucosa and is impaired in sepsis. Retinal microcirculation can be directly imaged by optical coherence tomography angiography (OCTA) during perfusion-deficit states such as sepsis, and other systemic haemodynamic disturbances such as acute coronary syndrome, and systemic inflammatory conditions such as inflammatory bowel disease. Conclusion Monitoring microcirculatory flow offers the potential to enhance monitoring in the care of critically ill patients, and imaging retinal blood flow during critical illness offers a potential biomarker for cerebral microcirculatory perfusion.

Artificial intelligence velocimetry and microaneurysm-on-a-chip for three-dimensional analysis of blood flow in physiology and disease

“…Scientific research over the past several decades has led to rapid advances in in vivo imaging techniques (12)(13)(14). Despite this progress, it is currently not feasible to observe in real time many in vivo biological processes in microcirculation, such as the rupture of a microaneurysm (MA) in the retinal microvasculature and the initiation and development of blood clots.…”

Stability of OCT and OCTA in the Intensive Therapy Unit Setting

“…An earlier study using Stratus OCT3 on 103 healthy volunteers found the RNFL of the right eye was 1.2-1.3 µm thicker than the left eye and concluded that the mean RNFL thickness in healthy individuals should not exceed a difference of 9-12 µm between eyes [40]. Because differences in retinal blood flow reflect differences in retinal structure across a variety of pathologies, including optic neuropathies, it is possible that this left-right difference in blood flow reflects the structural asymmetry [3].…”

“…Optical coherence tomography angiography (OCTA) images retinal and choroidal blood flow three-dimensionally by using moving red blood cells as the contrast medium, without the need for injectable contrast [2]. Critically ill patients with sepsis and systemic inflammatory response syndrome often have systemic microcirculatory defects, manifested as reduced functional capillary density, which reduces oxygen delivery and propagates organ dysfunction [3]. Retinal microcirculation is readily quantifiable and can be sequentially monitored non-invasively.…”

“…Retinal microcirculation is readily quantifiable and can be sequentially monitored non-invasively. Retinal neuronal and microvascular changes mirror systemic and cerebral pathology in health and disease, such as in Parkinson's and Alzheimer's Disease [3][4][5][6], and retinal and cerebral circulations share similar mechanisms of blood flow regulation [7], suggesting that retinal blood flow may serve as a surrogate for cerebral perfusion [3]. OCTA demonstrates retinal blood flow derangements in microvascular diseases, such as atrial fibrillation [8], acute coronary syndrome [9], systemic hypertensive crisis [10], inflammatory bowel disease [11], haemorrhagic shock [12,13], high-risk pregnancies [14], and preeclampsia [15].…”

Optical coherence tomography’s current clinical medical and dental applications: a review

“…1 OCT has quickly gained popularity among clinicians due to several advantages that include delivering quality images with quick imaging speed. 2 This technique has several clinical applications that include (but are not limited to) detection of diabetic macular edema, 3 epithelial mapping for refractive surgery, 4 diagnosing and managing patients with neuro-ophthalmic conditions, 5 imaging of retinal microcirculation to detect hemodynamic disturbances, 6 detection of age associated changes in teeth, 7 diagnosing dental caries 8 and tooth wear, 9 and post-treatment assessments in dentistry. 10 The aim of this review is to summarize the clinical applications of OCT in the field of medicine and dentistry, and highlight its potential advantages and disadvantages.…”